This invention relates to door opening and/or closing and/or latching devices and especially though not solely to devices which may be used in conjunction with home appliance doors, such as refrigerator doors to assist in opening and closing these doors.
A conventional door must be opened by physically pulling on the door and closed by physically pushing on the door. In order to maintain the door in a closed position a latch is often incorporated so that opening and closing then also involves physically connecting and disconnecting the latch mechanism.
In refrigerator cabinets, the doors there has long been a problem of holding the door closed in order that cooled air does not escape thereby warming and spoiling the contents. Refrigerator doors have been fitted with a gasket which is often formed from a plastic material which seals between the door and the door frame. The gasket often has a permanent magnetic strip incorporated therein which assists in holding and sealing the door to the door frame. The gasket has been designed to incorporate the aforementioned magnetic strip and has not, therefore, been designed with optimal thermal sealing properties in mind and this aspect of its design could be improved. Also, the fact that the magnet is positioned in the gap between the door and frame means that it provides a path for heat conduction into the refrigerator cabinet through this gap. In addition, the magnet necessitates the use of metal door frame surrounds in order that the magnet may be attracted to the door frame thus providing a further path for heat conduction from the interior of the refrigerator cabinet. Furthermore, the assembly of the magnetic strip in the door gasket is a source of assembly cost due to the time and labour required which could be eliminated. However, even when this magnetic gasket is used it is often still necessary to arrange the refrigerator cabinet so that the front is raised slightly above the level of the back ensuring that the door is always biassed towards a closed position. However, it is still possible for a user to have seemingly closed the door when in reality there is still a gap between the door and frame which the existing permanent magnet can not possibly close.
In an effort to overcome this problem some refrigerator manufacturers have developed devices which prevent refrigerator doors from resting in an almost closed position. An example of such a device is disclosed in U.S. Pat. No. 5,138,743 (assigned to White Consolidated Industries Inc. ) wherein the hinge pin is attached to the cabinet through a bracket and is provided with lobe shaped camming surfaces around the pin and complementary lobe shaped camming surfaces are also provided around an aperture in the door. The two camming surfaces arranged so that the door will tend to rotate to a position where the lobes fit together which is arranged to be where the door would ordinarily close or even beyond the normal closing position so that a closing force is always applied to the door when it meets the door frame.
Another problem in present refrigerator cabinet door designs (especially large doors) is that when the door has been closed and a good seal is established between the door and frame, it is necessary to supply a relatively large force to the door in order to open it. This is disadvantageous in modem home appliances which are expected to be easy to operate and, in the case of refrigerator doors, repeatedly and easily opened with a consistent force. A door which could be reliably closed without the need for the user to occasionally manually check that this is the case would also be an improvement.
Examples of improved door latching systems and door opening/closing systems which utilise a combination of permanent and electromagnets are disclosed in U.S. Pat. Nos. 3,635,511 (Waller), 3,647,165 (Whitla), 3,658,370 (Wang), 3,764,172 (Standke), 3,860,277 (Wang), 4,428,607 (Levine), 4,506,407 (Downey) and 5,293,020 (Han et al). However, none of the aforementioned systems are intended for use in refrigerator cabinets and do not incorporate the necessary user sensing hardware and associated logic. Furthermore, many of the systems disclosed require a mechanical latching mechanism in association with the magnetic components.
It is, therefore, an object of the present invention to provide a door opening, closing and/or holding system which will at least go someway towards overcoming the above disadvantages or which will at least provide the public with a useful choice.
In one aspect the invention consists in a door state changing apparatus for assisting a user to move a door between a closed state where the door is positioned adjacent a door frame and an open state comprising:
permanent magnet means on or attached to said door to provide a permanent magnetic field,
electromagnet means on or attached to said door frame adjacent said permanent magnet means when said door is in said closed state, which electromagnet means is energisable to provide a magnetic field in a first direction to reinforce said permanent magnetic field and energisable to provide a magnetic field in a second direction to oppose said permanent magnetic field,
door position detection means to detect the state of said door,
user interface means to detect the presence of a user attempting to alter the state of said door, and
control means which receives input from said door position detection means and said user interface means and provides a control signal to energise said electromagnet means to provide a magnetic field in said first direction if said user interface means indicates a user is attempting to alter the state of said door and said door position detection means indicates that said door is in said open state and provides a control signal to energise said electromagnet means to provide a magnetic field in said second direction if said user interface means indicates a user is attempting to alter the state of said and said door position detection means indicates that said door is in said closed state.
In a further aspect the invention consists in a home appliance including a cabinet and a door hingeably connected to said cabinet and closeable against a door frame said appliance including door state changing apparatus for assisting a user to move said door between a closed state and an open state where said door is positioned adjacent said door frame and an open state, said door state changing apparatus comprising:
permanent magnet means on or attached to said door to provide a permanent magnetic field,
electromagnet means on or attached to said door frame adjacent said permanent magnet means when said door is in said closed state, which electromagnet means is energisable to provide a magnetic field in a first direction to reinforce said permanent magnetic field and energisable to provide a magnetic field in a second direction to oppose said permanent magnetic field,
door position detection means are also provided to detect the state of said door,
user interface means to detect the presence of a user attempting to alter the state of said door, and
control means which receives input from said door position detection means and said user interface means and provides a control signal to energise said electromagnet means to provide a magnetic field in said first direction if said user interface means indicates a user is attempting to alter the state of said door and said door position detection means indicates that said door is in said open state and provides a control signal to energise said electromagnet means to provide a magnetic field in said second direction if said user interface means indicates a user is attempting to alter the state of said and said door position detection means indicates that said door is in said closed state.
In a still further aspect the invention consists in a refrigerator including door state changing apparatus as set forth above.
To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.